The invention relates initially to a synchronous linear electric motor with a secondary part containing several permanent magnets arranged in a certain pole grid, and with a primary part that can move relative to the secondary part and whose position relative to the secondary part can be determined by a travel measurement system.
The invention also relates to a method for determining the commutation offset in a synchronous linear electric motor.
In order to ensure a force of the synchronous linear motor that is constant over time, an angle of 90.degree. must be set between the field vector of the primary part and the field vector of the secondary part. This means that the motor control of the primary part must operate as a function of the current position of the location of the permanent magnet poles of the secondary part. Therefore, the motor control requires the current actual position values of the primary part relative to the secondary part. A travel measurement system is provided for the purpose, which supplies this information for motor control.
In synchronous motors in general, following mechanical assembly, there is initially no unambiguous relationship between the field vectors of the primary and secondary parts. This relationship is clearly established during the initial startup of the drive by determining the so-called commutation offset.